This game has felt to me like it favors monster groups with many models (e.g. bandits, goblins, etc. (but not fire imps because those just suck)) over monster groups with a small number of models (e.g. hybrid sentinels, shadow dragons, ettins, etc.).
I wonder if monster groups with only a small number of models were intentionally made to have lower than usual stats due to the reinforcement mechanic (e.g. one group of goblin archers is stronger than one group of shadow dragons). Some quests let the overlord reinforce open groups, and if the overlord got a shadow dragon with stats equivalent to a goblin archer group every turn, that would probably be too much.
Should descent have gone with a "reinforcement point" mechanic where quests that used open group reinforcements gave the overlord a certain amount of reinforcement points each turn? Those points could then be spent to purchase reinforcements and each monster card would show the number of reinforcement points required to purchase one monster from that group (e.g. spawning a goblin archer might cost 1 reinforcement point and spawning a shadow dragon might cost 2 or 3 reinforcement points)? Reinforcement points could not be banked unless the overlord did not have enough to purchase one model from their reinforcing open group (e.g. overlord has 4 reinforcement points. A shadow dragon costs 3 reinforcement points, so the overlord MUST spawn one shadow dragon during the reinforcement step).
Edited by The MechE